This invention is related to a machine capable of grinding and polishing both sides of one or more workpieces simultaneously, and a method for using the machine to grind and/or polish both sides of a plurality of workpieces simultaneously.
Many materials such as silicon, metals and glass require grinding and polishing of various surfaces before the materials can be utilized as intermediate or end products. Existing grinding and polishing machines often utilize rotating discs to simultaneously polish two sides of a workpiece simultaneously. Because the polishing plates rotate, uneven velocity profiles exist throughout the process area. This can cause uneven stock removal across the workpieces which may result in finished pieces with poor flatness and surface parallelism.
Most grinding and polishing machines utilized to grind two sides of a workpiece simultaneously employ abrasives to aid in polishing and finishing various types of workpieces. Typically these abrasives are applied to the workpieces through conduits in the polishing plates. Because the polishing plates rotate, complicated rotating connections are required between the stationary abrasive source and the rotating discs to enable polishing abrasives to be supplied to both sides of the workpieces. These connections are subject to failure which ultimately reduces the efficiency of the polishing machine.
The polishing and finishing rates of most newer polishing machines may be adjustable by adjusting the RPM of the polishing plates. Typically, an increase in the revolutions per minute of the polishing plate will result in a proportional increase in the polishing rate or grind rate of the workpieces. However, the plate velocity will vary across the radius of the workpiece with the outer portion of a polishing plate traveling at a higher velocity than the inner portion of the polishing plate. This disparity in plate velocity can cause a disparity in the ability of the polishing plate to uniformly polish or grind a workpiece. The problem is essentially due to the fact that the polishing plate rotates about a fixed axis.
Present methods of grinding and polishing workpieces generally are able to produce a satisfactory product at a satisfactory production rate. However, present methods suffer from problems related directly to the construction of rotating polishing and grinding machines. These problems include difficulties in supplying polishing abrasives to the workpieces, difficulties in maintaining a constant polishing velocity across a the surface of workpiece within a batch, and difficulties in finishing both sides of a workpiece simultaneously to a uniform finish.